The invention relates to a thickness planer and more specifically, to a thickness planer having a carriage locking mechanism that reduces vibration and movement of the carriage during a planing operation.
Planing is the removal of wood from a surface or face of a board so as to make it flat, uniform, and smooth. In woodworking, planing is a common operation that is used in manufacturing cabinets, tables and other wood products.
Conventional thickness planers include a base having four perpendicularly mounted columns. A carriage is supported on the support columns and includes a rotating cutting head. The cutting head has at least one cutting knife which, when rotated, removes a designated amount of material from a workpiece passing through the planer.
Most thickness planers include a lead screw for adjusting the height or distance of the carriage above the base. Since the cutting head is rotatably attached to the carriage, the height of the carriage determines the amount of material that is removed from the workpiece and thereby the thickness of the workpiece exiting the planer. The difference between the thickness of the workpiece entering the planer and the thickness of the workpiece exiting the planer is known as the depth of cut, which is the depth of the material that is removed by one pass of the workpiece through the thickness planer. To facilitate the movement of the workpiece through the planer, a motor-powered infeed roller pulls the workpiece into the planer, while an outfeed roller helps the workpiece to exit the planer. Conventional thickness planers also typically include an infeed shelf or table and an outfeed table that supports the workpiece as it is being fed and cut.
To provide versatility, the carriage is typically adjustable to different heights. However, during the cutting operation, it is preferred that the carriage be securely attached to the housing of the thickness planer. Otherwise, vibration and movement of the carriage during the planing operation may produce undesired “snipe” or localized variations in the workpiece thickness. This undesired vibration and movement is especially prevalent when the workpiece is entering or exiting the thickness planer, i.e. at the beginning and end of a cut. Accordingly, some conventional thickness planers include locks, which secure the carriage in position during operation.
There are different types of carriage locks. For example, U.S. Pat. No. 5,794,675 to Garcia discloses a carriage lock containing forks running the length of the support columns. The forks are deflected and sandwiched between the carriage and associated support columns to frictionally secure the carriage. Garcia, however, attempts to lock the carriage in line with the cutting head instead of locking the carriage at a location away from the cutting head. It has been found that the close proximity of the locking mechanism to the cutting head likely reduces stability when locking the carriage.
Another type of carriage lock is disclosed in U.S. Pat. No. 5,771,949 to Welsh et al. Welsh discloses various resiliently deflectable mechanisms having springs, levers, or more resiliently deflectable members to secure the carriage at a given height.
Existing carriage locks such as those described above, however, fail to produce a mechanical clamping action that reduces the amount of force necessary to lock the carriage, compared to the holding strength of the locks. Further, because existing carriage locks rely upon resiliently deflected members, these mechanisms fatigue over time and become less effective at securing the carriage.
Accordingly, there is a need for an improved carriage lock mechanism that overcomes the drawbacks of conventional units and reduces the amount of snipe in a workpiece by more securely holding the cutting head and the carriage in a desired position.